Noise, vibration and harshness (NVH) during operation of an automobile can greatly affect customer satisfaction with the vehicle. Accordingly, NVH considerations are now commonly taken into consideration during design and manufacture of automobiles. NVH results from vibration of various parts of the automobile, such as the engine (and engine mounts), body panels, chassis, exhaust piping, etc. The vibration can produce undesirable noise in the passenger compartment, and can be transmitted through components such as the seats, steering wheel, etc. to vehicle occupants. NVH can be particularly noticeable during idle.
One proposed solution to controlling NVH during idle involves consideration of certain natural frequencies of the vehicle. Through testing or other methods, natural frequencies are determined for various components of the vehicle. The control systems of the vehicle that govern idle engine speed are then designed taking the natural frequencies into consideration. For example, idle speed control is often implemented so that piston firing frequencies at idle do not amplify natural frequencies, for example by creating resonance. The inventors have recognized a problem with this solution, namely that the parameters of idle speed control are fixed at design time, and do not account for wear and break-in, or for dynamically changing conditions arising during operation of the vehicle.
Accordingly, the present disclosure provides a system and method of operating a vehicle powertrain that employs active control to reduce NVH, particularly during idle. The method includes selectively operating the powertrain in at least a non-idle condition and an idle condition; receiving vibration signals from a sensor disposed on an internal combustion engine; controlling spark timing of the internal combustion engine based on vibration signals received from the sensor; and during the idle condition, modifying a speed and/or a load of the internal combustion engine based on vibration signals received from the sensor.